1. Field of the Invention
This invention relates to aluminum and aluminum alloy for a fin and a heat exchanger having such a fin incorporated therein by brazing, the invention relates to more particularly, aluminum and aluminum alloy for a fin of which the desired characteristics, particularly, thermal conductivity and the like are highly improved in order to increase the effectiveness or cooling capacity of a heat exchanger, and the application of such aluminum and aluminum alloy material to a heat exchanger.
2. Description of the Prior Art
A heat exchanger having a fin of aluminum or aluminum alloy incorporated therein by brazing (hereinafter referred to as "Al heat exchanger") has been extensively used in various fields involving an automobile, an aircraft and the like. Such a heat exchanger generally comprises a passage means for flowing a refrigerant such as Freon, (Tradename, Fluorohydrocarbon made by Du Pont & Co., Inc.), water or the like therethrough (hereinafter referred to as "tube") and a fin for heat radiation. As the tube, an extruded perforated tube of a flat shape or a flat seam welded tube formed of a brazing sheet having an Al-Si brazing material cladded thereon is selectively used depending upon the use of the heat exchanger. Also, the fin is formed of a alloy sheet 3 comprising a core 1 and an Al-Si brazing clad material 2 cladded on each of both surfaces of the core 1 as shown in FIG. 1 or only the core.
An embodiment of the heat exchanger having a fin formed of Al or Al heat exchanger is shown in FIG. 2. More particularly, FIGS. 2A and 2B show an evaporator and a condenser, respectively, each of which comprises a flat extruded perforated tube 4 and a fin 5 formed of a brazing sheet 3 as shown in FIG. 1. FIG. 2C shows a radiator which comprises a flat seam welded pipe 6 formed of a brazing sheet having an Al-Si brazing material cladded on the outer surface thereof and an unclad fin 7. Such heat exchangers as described above each are assembled by bonding the pipe and corrugated fin together by flux brazing, vacuum brazing or brazing in an inert gas atmosphere at a temperature of about 600.degree. C. using the brazing material previously cladded on the pipe.
In such an Al heat exchanger manufactured by brazing as described above, a fin was typically manufactured using a sheet metal of 0.1-0.2 mm in thickness formed of Al-Mn alloy having good sagging resistance at a high temperature, for example, such as AA 3003 alloy (Registered alloy of Aluminum Association U.S.A. (AA)) (Al, Cu: 0.05-0.20%, Mn: 1.0-1.5 %) or AA 3203 alloy (Al, Mn: 1.0-1.5%). Alternatively, it is made of a sheet metal of 0.1-0.2 mm in thickness which comprises a core material of such Al-Mn alloy as described above and a brazing material of Al-Si alloy (Al, Si: 5-12%) or Al-Si-Mg alloy (Al, Si: 5-12%, Mg: 0.5-2%) cladded on both surfaces of the core material.
However, the fin formed of Al-Mn alloy such as AA 3003 alloy or AA 3203 alloy is somewhat inferior in thermal conductivity although it has good sagging resistance as described above, resulting in the deterioration of heat radiation of a heat exchanger using such a fin.
Recently, weight saving and miniaturization are desired in a heat exchanger, particularly, for an automobile. Further, not only the formation of a fin having a smaller thickness but an improvement in performance of a heat exchanger or effectiveness (e.g. cooling capacity) thereof is requested in the art.
Accordingly, it would be highly desirable to develop a fin for a heat exchanger which has sufficient heat conductivity, does not cause the settling or deformation of the fin during the bonding by brazing and is improved in a so-called sacrificial anode effect of effectively preventing the corrosion of a tube of a heat exchanger.